BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] The present invention relates to a construction machine such as a hydraulic excavator
having a work implement.
2. Description of the Related Art
[0002] A construction machine such as a hydraulic excavator has a work implement configured
with a plurality of front implement members such as a boom, an arm, and a bucket (work
tools), and a travel device for moving the construction machine, and an operator can
actuate the work implement and the travel device by operating operation levers.
[0003] Work by the construction machine at a construction site is determined by a design
drawing or the like. Since it is difficult to carry out operation as intended only
by a judgment of situation based on an operator's visual check, the operator is instructed
in an intended work plane by installing marks such as finishing stakes and tracing
tapes on the construction site.
[0004] Meanwhile, it takes labor to install many finishing stakes and tracing tapes on a
wide construction site and operator's skill is also necessary to pursue construction
work as intended. Against this backdrop, a system called machine guidance for providing
posture detection means such as angle sensors for front implement members and stroke
sensors for hydraulic cylinders in the construction machine, computing a current position
of a work point (for example, a claw tip of a bucket) on the basis of detected posture
information and dimensions of the work implement, and displaying a distance between
the obtained current position of the work point and a target work plane on a screen
by a drawing or a numerical value has recently come into widespread use. It is thereby
possible for the operator to easily grasp contents of the work.
[0005] Accuracy of the computed current position of the work point is influenced by parameters
such as the posture information and the dimensions of the work implement described
above. Examples of causes of a reduction of the accuracy include changes in characteristics
due to an individual difference of the sensors used for posture detection and a secular
factor, changes in the posture information due to misalignments of sensor mounting
positions during disassembly and reassembly of the work implement, and dimensional
changes due to manufacturing errors, backlash, and plastic deformation of the front
implement members. Owing to this, it is necessary to maintain the accuracy of computed
values by calibrating the aforementioned parameters at regular intervals so that the
computed values and true values match with one another for the current position of
the work point at a time of shipment of the construction machine, before starting
the work, or the like.
[0006] To address the need, there has been proposed a technique for setting measurement
values measured by an external measuring device as true values and calibrating parameters
for a construction machine on the basis of the measurement values (refer to, for example,
the specification of Japanese Patent No.
5823046) or to the family member
US2015330060 which discloses the preamble of claim 1.
SUMMARY OF THE INVENTION
[0007] According to the technique described in Japanese Patent No.
5823046, the aforementioned parameters are calibrated using the external measuring device.
Generally, however, the external measuring device becomes more expensive as accuracy
is higher and expertise is essential for handling. Owing to this, only limited operators
can carry out calibration work. Furthermore, the external measuring device is not
necessarily installable at whatever site where the construction machine is used and
is, therefore, unfavorable for calibration before start of the work.
[0008] An object of the present invention is to enable an operator to easily carry out calibration
work at every construction site with a view to maintaining accuracy for computing
a position of a work point of a construction machine.
[0009] The present application includes a plurality of means for attaining the above object.
As an example of the means, there is provided a construction machine including: a
vehicle main body; a multijoint type work implement that is attached to the vehicle
main body and configured with a plurality of front implement members; a plurality
of angle sensors that detect angles of the plurality of front implement members respectively;
and/or a controller, the controller including: an angle computing section that calculates
angles of the plurality of front implement members on the basis of output signals
from the plurality of angle sensors and angle conversion parameters; and a first work
point position computing section that calculates a position of a work point arbitrarily
set on the work implement on an operation plane of the work implement on the basis
of the angles of the plurality of front implement members calculated by the angle
computing section and dimension parameters of the plurality of front implement members.
In the construction machine, when the work implement is actuated in such a manner
that the work point is located at each of a plurality of positions on a linear datum
line set on the operation plane, the first work point position computing section calculates
a position of the work point at each of the plurality of positions, and the controller
includes: a calibration value computing section that calculates calibration values
of the angle conversion parameters, the dimension parameters, and a parameter of the
datum line on the basis of the position of the work point at each of the plurality
of positions calculated by the first work point position computing section; and a
parameter update section that reflects the calibration values calculated by the calibration
value computing section in computation by a corresponding computing section that is
one of the angle computing section and the first work point position computing section.
ADVANTAGE OF THE INVENTION
[0010] According to the present invention, it is possible to maintain accuracy for computing
a position of a work point of a construction machine since calibration work can be
easily carried out at every construction site.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011]
Fig. 1 is a side view of a hydraulic excavator 1 in which a calibration system is
mounted;
Fig. 2 simply shows a coordinate system and dimensions of the hydraulic excavator
1;
Fig. 3 is a schematic configuration diagram of a vehicle body control system 28, a
display system 29, and a calibration system 30 mounted in the hydraulic excavator
1;
Fig. 4 is a flowchart of a calibration process according to a first embodiment;
Fig. 5 is a side view of the hydraulic excavator 1 that assumes three types of calibration
postures according to the first embodiment;
Fig. 6 shows a display example of a display device 18 that assists an operator in
operating when the operator causes a work implement 3 to assume a calibration posture;
Fig. 7 is a side view of the hydraulic excavator 1 according to a second embodiment;
Fig. 8 is a flowchart of a calibration process according to a third embodiment; and
Fig. 9 is a side view of the hydraulic excavator 1 according to a third embodiment.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0012] A calibration system for a construction machine according to embodiments of the present
invention will be described hereinafter with reference to the drawings while taking
a hydraulic excavator as an example.
<First Embodiment>
[0013] In a first embodiment, a point laser irradiator 47 (refer to Fig. 5) having a function
of measuring a gradient with respect to a horizontal plane is used as a datum line
creation device that defines a line (datum line 51) on which a bucket claw tip is
located on a construction site or the like.
[0014] Fig. 1 is a side view of a hydraulic excavator 1 in which a calibration system is
mounted according to the present invention. The hydraulic excavator 1 includes a vehicle
main body 2 that has an upper swing structure 4 and a lower travel structure 5, and
a multijoint type work implement (front work implement machine) 3 that is attached
to the upper swing structure 4 and configured with a plurality of front implement
members (link members) 6, 7, and 8.
[0015] The work implement 3 includes a boom 6 that is rotatably attached to the upper swing
structure 4 via a boom pin 19, an arm 7 that is rotatably attached to a tip end of
the boom 6 via an arm pin 20, and a bucket 8 that is rotatably attached to a tip end
of the arm 7 via a bucket pin 21. The work implement 3 also includes a boom cylinder
9, an arm cylinder 10, and a bucket cylinder 11 that are hydraulic cylinders (hydraulic
actuators) for driving the boom 6, the arm 7, and the bucket 8. In the present specification,
the bucket 8 is located on a tip end of the work implement 3 configured with the plurality
of front implement members 6, 7, and 8 and is, therefore, often referred to as "tip
end front implement member."
[0016] The lower travel structure 5 includes a left travel motor 15a, a right travel motor
15b, and left and right crawler belts (endless tracks) 14a and 14b driven by the travel
motors 15a and 15b, respectively. The travel motors 15a and 15b are driven to rotate
the crawler belts 14a and 14b, whereby the hydraulic excavator 1 travels. The lower
travel structure 5 is not limited to the crawler type shown in Fig. 1 but may be a
wheel type having a plurality of wheels.
[0017] The upper swing structure 4 is swingably attached to an upper portion of the lower
travel structure 5 via a slewing ring 16 and driven to swing by a swing drive device
(swing motor) 13. A cab 12, a hydraulic pump (not shown) delivering a hydraulic working
fluid for the hydraulic actuators, a prime mover (for example, an engine or a motor)
(not shown) for driving the hydraulic pump, and devices such as computers that include
a vehicle body control controller 31, a display controller 37, and a calibration controller
45 are mounted in the upper swing structure 4.
[0018] A vehicle body operating device 17 that outputs an operation signal in response to
an operation amount and a display device (for example, a liquid crystal display (LCD))
18 on which various information is displayed are provided in the cab 12. The operation
signal is output by operator's operating the vehicle body operating device 17. The
boom cylinder 9, the arm cylinder 10, the bucket cylinder 11, the swing drive device
13, and the travel motors 15a and 15b can be driven on the basis of the operation
signal.
[0019] In the present embodiment, a device provided with a plurality of levers that include
a first operation lever for instructing an operator on raising and lowering of the
boom 6 and dumping and crowding of the bucket 8, a second operation lever for instructing
the operator on dumping and crowding of the arm 7 and left and right swinging of the
upper swing structure 4, a first travel lever for instructing the operator on normal
rotation and reverse rotation of the travel motor 15a, a second travel lever for instructing
the operator on normal rotation and reverse rotation of the travel motor 15b (all
of which are not shown) is mounted as the vehicle body operating device 17. The first
operation lever and the second operation lever are double-compound multifunction operation
levers. Operating the first operation lever forward and backward corresponds to the
raising and lowering of the boom 6, and operating the first operation lever leftward
and rightward corresponds to the crowding and dumping of the bucket 8. Operating the
second operation lever forward and backward corresponds to the dumping and crowding
of the arm 7, and operating the second operation lever leftward and rightward corresponds
to the left and right rotation of the upper swing structure 4. When one lever is operated
in an oblique direction, two corresponding actuators operate simultaneously. The first
travel lever and the second travel lever are single function operation levers. Operating
the first travel lever forward and backward corresponds to the normal rotation and
reverse rotation of the travel motor 15a, and operating the second travel lever forward
and backward corresponds to the normal rotation and reverse rotation of the travel
motor 15b.
[0020] The vehicle body operating device 17 is provided with an operation amount sensor
(not shown) that detects operation amounts of the first and second operation levers
and the first and second travel levers and that transmits detection signals thereof
to the vehicle body control controller 31.
[0021] Fig. 2 simply shows a coordinate system and dimensions of the hydraulic excavator
1.
[0022] The coordinate system {Xf, Yf, Zf} of the hydraulic excavator 1 sets a center of
the boom pin 19 as an origin. A Zf axis is set in parallel to a central axis of the
slewing ring 16 and an upward direction is assumed as a positive direction of the
Zf axis. An Xf axis is set perpendicular to the Zf axis on a plane (operation plane)
on which a bucket claw tip 22 (work point 23) is movable, and a forward direction
of the upper swing structure 4 is assumed as a positive direction of the Xf axis.
A Yf axis, which is not shown, is set in accordance with a right-handed system. The
Yf axis is thereby an axis perpendicular to paper of Fig. 2 and a front side of the
paper is assumed as a positive direction of the Yf axis.
[0023] A length Lbm of the boom 6 is a length from the boom pin 19 to the arm pin 20, a
length Lam of the arm 7 is a length from the arm pin 20 to the bucket pin 21, and
a length Lbk of the bucket 8 is a length from the bucket pin 21 to the bucket claw
tip 22. It is assumed that a center of the bucket claw tip 22 in a width direction
is the work point 23. It is assumed that a counterclockwise direction of the boom
6, the arm 7, and the bucket 8 about the Yf axis is a positive rotation direction
thereof. It is noted that the work point 23 may be set to a point other than the center
in the width direction as long as the point is a point in the width direction of the
bucket 8.
[0024] The hydraulic excavator 1 is provided with a first rotation angle sensor 25, a second
rotation angle sensor 26, and a third rotation angle sensor 27 as angle sensors that
detect angles of the plurality of front implement members 6, 7, and 8 that configure
the work implement 3, respectively.
[0025] The first rotation angle sensor 25 attached to the upper swing structure 4 is, for
example, a rotary potentiometer and detects a relative angle θbm of the boom 6 to
the upper swing structure 4 as an analog signal Vbm. The second rotation angle sensor
26 attached to the boom 6 is, for example, a rotary potentiometer and detects a relative
angle θam of the arm 7 to the boom 6 as an analog signal Vam. The third rotation angle
sensor 27 attached to the arm 7 is, for example, a rotary potentiometer and detects
a relative angle θbk of the bucket 8 to the arm 7 as an analog signal Vbk.
[0026] A longitudinal tilt angle sensor 24 attached to the upper swing structure 4 is, for
example, an inertial measurement unit (IMU) and detects an angle θpitch of the Zf
axis with respect to a gravity direction about the Yf axis. It is assumed that a counterclockwise
direction of the angle θpitch is a positive direction.
[0027] Fig. 3 is a schematic configuration diagram of a vehicle body control system 28,
a display system 29, and a calibration system 30 mounted in the hydraulic excavator
1.
[Vehicle body control system 28]
[0028] The vehicle body control system 28 has the vehicle body operating device 17, the
vehicle body control controller (controller) 31, a hydraulic control system 32, the
boom cylinder 9, the arm cylinder 10, the bucket cylinder 11, the swing motor 13,
and the travel motors 15a and 15b.
[0029] The vehicle body control controller 31 is a computer that has an input/output section
35 configured with an A/D converter, a D/A converter, a digital input/output device,
or the like, a computing section 36 such as a CPU, and a storage section (not shown)
such as a ROM or a RAM.
[0030] The input/output section 35 of the vehicle body control controller 31 receives signals
input from the vehicle body operating device 17 and the hydraulic control system 32,
transmits the signals to the computing section 36, and transmits a computation result
of the computing section 36 to the hydraulic control system 32.
[0031] The computing section 36 of the vehicle body control controller 31 computes a command
value to the hydraulic control system 32 on the basis of the operation amounts transmitted
from the operation amount sensor of the vehicle body operating device 17 and a state
amount of the hydraulic control system 32.
[0032] The hydraulic control system 32 is a system that controls an amount of the hydraulic
working fluid allocated to the actuators such as the boom cylinder 9, the arm cylinder
10, the bucket cylinder 11, the swing motor 13, and the travel motors 15a and 15b
for driving the actuators. The hydraulic control system 32 is configured with, for
example, the engine, the hydraulic pump driven by the engine, a hydraulic control
valve that controls a flow rate and a direction of the hydraulic working fluid supplied
to each hydraulic actuator, and the like. The hydraulic control system 32 controls
the hydraulic actuators 9 to 11, 13, and 15 on the basis of the command value computed
by the vehicle body control controller 31.
[Display system 29]
[0033] The display system 29 has the display controller 37, a display operating device 38,
the longitudinal tilt angle sensor 24, and the first to third rotation angle sensors
25 to 27.
[0034] The display controller 37 is a computer that has an input/output section 39 configured
with an A/D converter, a D/A converter, a digital input/output device, or the like,
a computing section 40 (40a, 40b, 40c) such as a CPU, and a storage section 41 such
as a ROM or a RAM.
[0035] The input/output section 39 of the display controller 37 receives operation information
input from the display operating device 38, the analog signals (output signals) input
from the longitudinal tilt angle sensor 24 and the first to third rotation angle sensors
25 to 27, and calibrated parameters input from the calibration controller 45. The
input/output section 39 transmits the operation information, the analog signals (output
signals), and the calibrated parameters to the computing section 40 (40a, 40b, 40c).
Furthermore, the input/output section 39 transmits a computation result of the computing
section 40 (40a, 40b, 40c) to the display operating device 38 and the calibration
controller 45.
[0036] The computing section 40 of the display controller 37 functions as an angle computing
section 40a, a first work point position computing section 40b, and a work information
computing section 40c on the basis of a program stored in the storage section 41.
[0037] The storage section 41 of the display controller 37 stores angle conversion parameters,
vehicle body dimension parameters, and target plane information. The angle conversion
parameters include coefficients (αbm, βbm, αam, βam, αbk, and βbk (to be described
later)) in equations for converting the analog signals from the first to third rotation
angle sensors 25 to 27 into angles. The vehicle body dimension parameters include
the length Lbm of the boom 6, the length Lam of the arm 7, and the length Lbk of the
bucket 8 described above. The target plane information includes at least one coordinate
information on a cross-section of a plane on which the hydraulic excavator 1 carries
out work on an Xf-Zf plane.
[Angle computing section 40a]
[0038] The angle computing section 40a converts the analog signals Vbm, Vam, and Vbk input
to the input/output section 39 from the first to third rotation angle sensors 25 to
27 into angles θbm, θam, and θbk. For example, computation for converting the analog
signals Vbm, Vam, and Vbk into the angles θbm, θam, and θbk is performed using linear
equations. The angle computing section 40a according to the present embodiment calculates
the angles θbm, θam, and θbk as represented by the following Equations (1) to (3)
on the basis of the analog signals Vbm, Vam, and Vbk from the first to third rotation
angle sensors 25 to 27 and the angle conversion parameters αbm, βbm, αam, βam, αbk,
and βbk stored in the storage section 41 for converting these analog signals into
the angles θbm, θam, and θbk.
[First work point position computing section 40b]
[0039] The first work point position computing section 40b computes a position Pd = [Xd,
Yd, Zd] of the work point 23 in the coordinate system {Xf, Yf, Zf} of the hydraulic
excavator 1. The first work point position computing section 40b executes this computation
as represented by the following Equations (4) to (6) on the basis of the angles (θbm,
θam, and θbk) computed by the angle computing section 40a and the vehicle body dimension
parameters (Lbm, Lam, and Lbk) stored in the storage section 41. In the present specification,
the coordinates [Xd, Yd, Zd] of the work point 23 computed by the first work point
position computing section 40b are often referred to as a first Xf coordinate, a first
Yf coordinate, and a first Zf coordinate to distinguish the coordinates [Xd, Yd, Zd]
from coordinates of the work point 23 computed by a second work point position computing
section 49b to be described later.
[0040] The work information computing section 40c computes numerical information and display
information indicating a position relationship between the work point 23 and a target
plane on the basis of the operation information from the display operating device
38, a computation result of the first work point position computing section 40b, and
the target plane information stored in the storage section 41.
[0041] The display operating device 38 has an operation section 43 and a display section
44. The operation section 43 is, for example, a switch. By operating this switch,
the operator performs a changeover of the display information displayed on the display
device 18 and a setting of the target plane information stored in the storage section
41 of the display controller 37. The display section 44 is, for example, a liquid
crystal display and the computation result of the computing section 40 is displayed
on the display section 44 so that the operator confirms contents of the work.
[Calibration system 30]
[0042] The calibration system 30 is a system that calibrates the first to third rotation
angle sensors 25 to 27 by calibrating the parameters (angle conversion parameters,
dimension parameters, and the like) used by the angle computing section 40a and the
first work point position computing section 40b at a time of computing the position
of the work point 23. The calibration system 30 includes the calibration controller
45, a calibration operating device 46, and a datum line creation device 47.
[Datum line creation device 47]
[0043] The datum line creation device 47 is a device that creates the datum line 51 which
is the line on which the work point 23 is located at a time of calibration work and
that can acquire an angle θline of the datum line 51 with respect to a horizontal
plane as shown in Fig. 5. For example, a point laser irradiator having the function
of measuring a gradient with respect to the horizontal plane can be used as the datum
line creation device 47. A radiated laser beam may be not only a point laser beam
but also a line laser beam. If the laser beam is the latter, the datum line 51 is
always visible from the operator within the cab 12, so that the work point 23 can
be easily located on the datum line 51. In the present embodiment, the datum line
creation device 47 is fixed onto a ground by a tripod and creates the datum line 51
as shown in Fig. 5. A tilt of the datum line 51 with respect to the Xf-Zf plane defined
for the hydraulic excavator 1 is defined by a tangent (tan(θline - θpitch)) of a difference
between θpitch detected by the tilt angle sensor 24 and θline.
[0044] The calibration operating device 46 has an operation section 52 and a display section
53. The operation section 52 is, for example, a switch. By operating this switch,
the operator performs a changeover of the display information displayed on the display
device 18, a setting and an update of the angle conversion parameters and the vehicle
body dimension parameters stored in the storage section 41 of the display controller
37, a setting of information on the datum line 51 stored in a storage section 50 of
the calibration controller 45, a confirmation when the hydraulic excavator 1 assumes
a calibration posture for locating the work point 23 on the datum line 51, and the
like. The display section 53 is, for example, a liquid crystal display or a loudspeaker,
and displays contents of the calibration work procedures and a computation result
of a computing section 49 shown to the operator.
[Calibration controller 45]
[0045] The calibration controller 45 is a computer that has an input/output section 48 such
as a digital input/output device, the computing section 49 such as a CPU, and the
storage section 50 such as a ROM or a RAM.
[0046] The computation result of the computing section 40 of the display controller 37,
and the angle conversion parameters, the vehicle body dimension parameters, and the
like stored in the storage section 41 of the display controller 37 are input to the
input/output section 48 of the calibration controller 45. The input/output section
48 transmits the input computation result and parameters to the computing section
49. Furthermore, the input/output section 48 transmits a computation result of the
computing section 49 to the display controller 37 as appropriate to display the computation
result on the display device 18.
[0047] The storage section 50 of the calibration controller 45 stores the datum line information.
The datum line information is information necessary to define the datum line 51 on
the Xf-Zf plane. The datum line information includes an equation (linear equation
for Xf and Zf (refer to Equation (11)) indicating the datum line 51 on the Xf-Zf plane,
and line parameters including the tilt (tanθ) and an intercept (Zline) of the datum
line 51 on the Xf-Zf plane. As the datum line 51, an arbitrary line can be selected
on the Xf-Zf plane if the front work implement 3 can be moved so that the work point
23 is located at a plurality of positions on the datum line 51. The datum line information
according to the present embodiment includes the angle θline of the datum line 51
with respect to the horizontal plane about the Yf axis. A counterclockwise direction
of the angle θline about the Yf axis is assumed as a positive direction and the angle
θline can be acquired from an output from the datum line creation device 47.
[0048] The computing section 49 of the calibration controller 45 functions as the second
work point position computing section 49a, a calibration value computing section 49b,
and a parameter update section 49c on the basis of a program stored in the storage
section 50.
[Second work point position computing section 49a]
[0049] The second work point position computing section 49a is a section that calculates
a second Zf coordinate of the work point 23 by inputting the first Xf coordinate of
the work point 23 calculated by the first work point position computing section 40b
when the work point 23 is located at an arbitrary point (referred to as "datum point")
on the datum line 51 into the equation (linear equation for Xf and Zf) indicating
the datum line 51.
[Calibration value computing section 49b]
[0050] The calibration value computing section 49b is a section that calculates calibration
values of arbitrary parameters included in the angle conversion parameters, the dimension
parameters, and the line parameters on the basis of coordinate values (first Xf coordinates,
first Zf coordinates) of the work point 23 at a plurality of datum points calculated
by the first work point position computing section 40b and the equation (linear equation
for Xf and Zf) indicating the datum line 51. More specifically, the calibration value
computing section 49b calibrates the calibration values of the abovementioned parameters
using the fact that the coordinate values (first Xf coordinates, first Zf coordinates)
of the work point 23 at the plurality of datum points calculated by the first work
point position computing section 40b can satisfy the equation (linear equations for
Xf and Zf) indicating the datum line 51. In the present embodiment, the calibration
value computing section 49b calculates the calibration values of the angle conversion
parameters αbm, βbm, αam, βam, αbk, and βbk and the calibration value of the intercept
Zline of the datum line 51.
[Parameter update section 49c]
[0051] The parameter update section 49c is a section that performs a process for reflecting
the calibration values of the arbitrary parameters calculated by the calibration value
computing section 49b in computation by the corresponding computing section 40 out
of the angle computing section 40a and the first work point position computing section
40b.
[Flowchart of calibration process]
[0052] Fig. 4 is a flowchart of a calibration process according to the first embodiment,
and shows an example of a computation process when the parameters to be calibrated
are assumed as the angle conversion parameters αbm, βbm, αam, βam, αbk, and βbk.
[0053] First, in Step S1, the computing section 49 sets initial values of αbm, βbm, αam,
βam, αbk, and βbk. The set initial values are theoretical values of the angle conversion
parameters obtained from specified values, an assembly drawing, and the like of the
first to third rotation angle sensors 25 to 27. It is noted that Step S1 can be omitted
if the values of αbm, βbm, αam, βam, αbk, and βbk are already set.
[0054] In Step S2, the computing section 49 displays on the display device 18 a message
for urging the operator to input the angle θline of the datum line 51 with respect
to the horizontal plane obtained from the datum line creation device 47. The operator
inputs the angle θline via the operation section 52 of the calibration operating device
46, and the computing section 49 acquires the tilt angle θpitch of the vehicle body
Zf axis with respect to the gravity direction about the Yf axis at this time from
the longitudinal tilt angle sensor 24.
[0055] In Step S3, the computing section 49 starts repetition processes of Steps S4 to S6
for acquiring measurement values in a plurality of calibration postures. The number
N of the repetition processes needs to be at least equal to the number of the parameters
for which the calibration values are calculated. In the present embodiment, the number
N may satisfy N ≥ 7 since the parameters for which the calibration values are calculated
are the six angle conversion parameters and one Zf intercept of the datum line 51.
In the present embodiment, it is assumed that N = 7.
[0056] In Step S4, the computing section 49 displays on the display device 18 a message
for urging the operator to cause the work implement 3 to assume a calibration posture
and to operate the operation section 52 in the state. The calibration posture is an
arbitrary posture of the work implement 3 for locating the work point 23 on the datum
line 51.
[0057] Fig. 5 is a side view of the hydraulic excavator 1 that assumes three types of calibration
postures. In all the calibration postures in Fig. 5, the work point 23 is located
on the datum line 51. All the N calibration postures assumed by the work implement
3 should differ from one another.
[0058] Fig. 6 shows a display example of display of the display device 18 that assists the
operator in operating when the operator operates the operating device 17 to cause
the work implement 3 to assume a calibration posture in Step S4. On this display screen,
all of output values (voltage values) of the analog signals Vbm[p], Vam[p], and Vbk[p]
from the first to third rotation angle sensors 25 to 27 acquired by actuating the
work implement 3 so that the work point 23 is located at the plurality of positions
on the datum line 51 during the previous repetition processes of Steps S4 to S6 are
displayed. Even if one of the boom 6, the arm 7, and the bucket 8 is not driven, the
work implement 3 can take all the different calibration postures. Nevertheless, if
the boom 6, the arm 7, and the bucket 8 are largely moved in respective movable ranges,
it is possible to optimize the calibration result in the entire movable ranges. Owing
to this, as shown in Fig. 6, the voltage values of the analog signals from the first
to third rotation angle sensors 25 to 27 acquired in the previous repetition processes
are displayed on analog gauges from 0 to 5 volts in broken lines, while current voltage
values of the analog signals are displayed on the gauges in arrows and displayed digitally
in lower portions of the gauges. The display device 18 thereby assists in making the
postures of the boom 6, the arm 7, and the bucket 8 different in the N calibration
postures.
[0059] In Step S5, the operator operates the operation section 52 at timing at which the
operator operates the vehicle body operating device 17 to drive the boom 6, the arm
7, and the bucket 8 to assume the calibration posture. With operator's operating the
operation section 52 as a trigger, the computing section 49 measures the analog signals
Vbm[p], Vam[p], Vbk[p] from the first to third rotation angle sensors 25 to 27 in
a p-th (1 ≤ p ≤ N) repetition process.
[0060] In Step S6, the computing section 49 determines whether the repetition process starting
at Step S3 has been performed the N times. When determining that the repetition process
has been performed the N times, the computing section 49 ends the repetition processes
and proceeds to Step S7; otherwise, the computing section 49 increments p by 1, returns
to Step S4, and continues the repetition processes.
[0061] In Step S7, the computing section 49 starts repetition processes of Steps S8 to S13
for obtaining the parameters and the Zf intercept of the datum line 51 to be calibrated
by a nonlinear least-squares method. The repetition processes are continued until
a condition to be described later is satisfied.
[0062] In Step S8, the angle computing section 40a performs angle computation, as represented
by Equations (1) to (3), on the measurement values of the analog signals from the
first to third rotation angle sensors 25 to 27 for the N times, thereby obtaining
angle computed values θbm[p], θam[p], and θbk[p] (1 ≤ p ≤ N) of the boom 6, the arm
7, and the bucket 8.
[0063] In Step S9, the first work point position computing section 40b performs work point
position computation, as represented by Equations (4) and (6), on the angle computed
values for the N times in Step S8, thereby obtaining work point position computed
values Xd[p] and Zd[p] (1 ≤ p ≤ N) on the Xf-Zf plane.
[0064] In Step S10, the second work point position computing section 49b determines whether
calibration is necessary. Determination whether calibration is necessary can be omitted
once the second work point position computing section 49b determines that calibration
is "necessary." When an error of the work point position computed values that are
supposed to be present on the datum line 51 from the coordinates of the datum line
51 is large, the second work point position computing section 49b determines that
calibration is necessary. When the error is small, the second work point position
computing section 49b determines that calibration is unnecessary. The determination
whether calibration is necessary in Step S10 will be described in detail below.
[0065] A linear equation that indicates probable values of a point (Xb, Zb) on the datum
line 51 on the Xf-Zf plane is represented by the following Equation (11). In Equation
(11), it is assumed that Zline is the Zf intercept of the datum line 51 on the Xf-Zf
plane shown in Fig. 5, and that initial values of the point (Xb, Zb) are (Xb, Zb)
= (Xd[1], Zd[1]), which are numerical values obtained by rearranging Equation (11).
[0066] The second work point position computing section 49b calculates the second Zf coordinate
by inputting the first Xf coordinate (Xd[p]) into Equation (11) for every p (1 ≤ p
≤ N) .
[0067] When it is assumed that a permissible height error of the work point position computed
value is ΔZ and the following Expression (12) is satisfied for every p (1 ≤ p ≤ N)
(that is, when a magnitude of a difference between the first Zf coordinate (Zd[p])
and the second Zf coordinate does not exceed ΔZ), then the second work point position
computing section 49b determines that calibration is unnecessary and the computing
section 49 ends the flowchart of Fig. 4. Conversely, when Expression (12) is not satisfied
for some p, then the second work point position computing section 49b determines that
calibration is necessary, the computing section 49 proceeds to Step S11, and the calibration
value computing section 49c computes the calibration values.
[0068] In Steps S11 to S13, the calibration value computing section 49c calculates the angle
conversion parameters and the Zf intercept of the datum line 51 to be calibrated by
numerical analysis in such a manner that an evaluation value ("evaluation equation
F" to be described later) indicating a dissociation degree (separation degree) between
the first Zf coordinate and the second Zf coordinate at the same datum point on the
datum line 51 can be minimized. Processes in Steps S11 to S13 will be described in
detail below.
[0069] In Step S11, the calibration value computing section 49c obtains the evaluation function
F for the work point position computed value (first Zf coordinate) and the datum line
51 (second Zf coordinate). The evaluation function F is assumed as a residual square
sum between the work point position computed value and the datum line 51, and the
calibration value computing section 49c executes the following Equation (13).
[0070] In Step S12, the calibration value computing section 49c performs computation for
updating the angle conversion parameters and the Zf intercept of the datum line 51
to be calibrated in such a manner that the evaluation function F can be minimized.
The calibration value computing section 49c is assumed to use, for example, a steepest-descent
method. The parameters and the Zf intercept of the datum line 51 to be calibrated
in a q-th (1 ≤ q) repetition process are collected into a vector V[q] = [αbm βbm αam
βam αbk βbk Zline]. The calibration value computing section 49c executes the following
Equation (14) to obtain a Jacobian J from the residual square sum F and the vector
V[q].
[0071] Each partial derivative is computed by a discretization scheme such as a difference
method. The calibration value computing section 49c executes the following Equation
(15) to obtain an updated vector V[q+1] used in a next repetition process from the
Jacobian J and a learning rate η (η > 0) that is a parameter for determining a convergence
speed.
[0072] In Step S13, the calibration value computing section 49c performs convergence determination.
While assuming that elements in the vector V[q] are vk[q] (1 ≤ k ≤ 7) and a convergence
determination threshold is τv, the calibration value computing section 49c executes
the following Expression (16).
[0073] When a condition of Expression (16) is satisfied, the computing section 49 proceeds
to Step S14. Conversely, when the condition of Expression (16) is not satisfied and
time of the repetition processes exceeds set time, the computing section 49 proceeds
to Step S15. Otherwise, the computing section 49 increments q by 1, returns to Step
S8, and continues the repetition processes.
[0074] In Step S14, the parameter update section 49c extracts the calibrated parameters
αbm, βbm, αam, βam, αbk, and βbk from the convergent vector V[q+1], stores the calibrated
parameters in the storage section 41 of the display controller 37 via the input/output
section 48 of the calibration controller 45, and reflects the calibrated parameters
in Computing Equations (1) to (3) used by the angle computing section 40a, and the
computing section 49 ends the flowchart of Fig. 4.
[0075] In Step S15, the computing section 49 determines that the vector V[q+1] is not convergent,
determines a cause of non-convergence from a computation result of a last repetition
process. When a coping method is discovered from the determined cause, the computing
section 49 displays the coping method on the display section 53 of the calibration
operating device 46, and ends the flowchart of Fig. 4.
[Operations and effects]
[0076] When it is necessary to carry out the calibration work on the angle sensors 25 to
27 in the hydraulic excavator 1 configured as described above, the operator first
installs the datum line creation device 47 on the construction site or the like, creates
the datum line 51 in a range in which the claw tip 22 of the bucket 8 reaches the
datum line 51, and acquires the angle θline that is the gradient of the datum line
51. When the operator gets on board in the hydraulic excavator 1 and inputs the angle
θline of the datum line 51 via the operation section 52, the tilt (gradient) of the
datum line 51 on the Xf-Zf plane is defined by the difference between this angle θline
and the tilt angle θpitch detected by the longitudinal tilt angle sensor 24.
[0077] Subsequently, the operator operates the operation section 52 in a state in which
the operator operates the vehicle body operating device 17 and thereby operates the
work implement 3 to locate the claw tip 22 (work point 23) on the datum line 51, and
the computing section 49 measures the analog signals Vbm, Vam, and Vbk output from
the angle sensors 25 to 27. Determination whether the work point 23 is present on
the datum line 51 is performed by operator's visually confirming whether a point laser
beam emitted from the datum line creation device 47 is radiated on the work point
23 on the bucket 8. This determination is repeated the seven times (N times) in the
different calibration postures. At that time, by operator's referring to the screen
of Fig. 6 displayed on the display device 18, it is possible to make the postures
of the boom 6, the arm 7, and the bucket 8 different among the seven calibration postures.
[0078] When seven analog signal measurements are over, the calibration controller 45 calculates
the calibration values of the angle conversion parameters αbm, βbm, αam, βam, αbk,
and βbk and the intercept Zline by performing the numerical analysis in such a manner
that the error between the coordinate value (first Zf coordinate) of the work point
23 and the linear equation (second Zf coordinate) indicating the datum line 51 is
closer to zero. The parameters used by the angle computing section 40a are then updated
to the calculated calibration values and the calibration is automatically completed.
[0079] As described so far, according to the present embodiment, the work point 23 is made
to be located at the plurality of datum points on the datum line 51, whereby the numerical
analysis is performed in such a manner that the error between the coordinate value
of the work point 23 and the linear equation indicating the datum line 51 is closer
to zero and the parameters are automatically calibrated. Therefore, it is possible
to greatly shorten calibration work time without the need of measurement and the like
of the coordinates of the position of the work point 23 during the calibration work.
[0080] Moreover, according to the present embodiment, a single operator can carry out work
for installing the datum line creation device 47 and work for locating the work point
23 at the plurality of datum points on the datum line 51 without delay. Therefore,
operators supposed to be involved in the calibration can be deployed to other work,
which can contribute to improving work efficiency on the entire construction site.
<Second Embodiment>
[0081] A second embodiment of the present invention will next be described. The second embodiment
differs from the first embodiment in that not only the gradient of the datum line
51 created by the datum line creation device 47 but also the position thereof is known.
[0082] Fig. 7 is a side view of the hydraulic excavator 1 according to the second embodiment.
The datum line creation device 47 according to the present embodiment is the point
laser irradiator similar to the datum line creation device 47 according to the first
embodiment. However, the datum line creation device 47 according to the present embodiment
is fixed to the hydraulic excavator 1 via a jig attached to the hydraulic excavator
1. The datum line creation device 47 is thereby always present at a fixed position
in a fixed posture in the coordinate system {Xf, Yf, Zf} of the hydraulic excavator
1. Owing to this, an angle θ'line of the datum line 51 (that is, a tilt of the datum
line 51) with respect to the Xf axis about the Yf axis on the Xf-Zf plane and the
Zf intercept Zline are known as the datum line information. The present embodiment
can, therefore, facilitate computing the calibration values, compared with the first
embodiment.
[0083] A hardware configuration of the hydraulic excavator 1 according to the present embodiment
is the same as that according to the first embodiment except for the above respect.
Differences of the hydraulic excavator 1 according to the present embodiment from
that according to the first embodiment will be described below. The parameters to
be calibrated in the present embodiment are assumed as the angle conversion parameters
αbm, βbm, αam, βam, αbk, and βbk similarly to the first embodiment, and a flow of
the flowchart is the same as that shown in Fig. 4. Here, processes (steps) in the
flowchart different from those according to the first embodiment will be mainly described
with reference to Fig. 4, while it is assumed that processes (steps) not described
below are performed similarly to those according to the first embodiment.
[0084] In Step S2, the computing section 49 inputs therein the operator inputs the angle
θ'line of the datum line 51 with respect to the coordinate system of the hydraulic
excavator 1 and the Zf intercept Zline of the datum line 51 that are stored in the
storage section 50 in advance.
[0085] In Step S3, the computing section 49 starts repetition processes of Steps S4 to S6
for acquiring measurement values in a plurality of calibration postures. In the present
embodiment, the number N may satisfy N ≥ 6 since the parameters for which the calibration
values are calculated are the six angle conversion parameters. In the present embodiment,
it is assumed that N = 6.
[0086] In Step S10, the second work point position computing section 49b determines whether
calibration is necessary. The determination whether calibration is necessary in Step
S10 according to the present embodiment will be described in detail below.
[0087] A linear equation that indicates probable values of the point (Xb, Zb) on the datum
line 51 on the Xf-Zf plane is represented by the following Equation (21).
[0088] When it is assumed that the permissible height error of the work point position computed
value is ΔZ and the following Expression (22) is satisfied for every p (1 ≤ p ≤ N)
(that is, when the magnitude of the difference between the first Zf coordinate (Zd[p])
and the second Zf coordinate does not exceed ΔZ), then the second work point position
computing section 49b determines that calibration is unnecessary and the computing
section 49 ends the flowchart of Fig. 4. Conversely, when Expression (22) is not satisfied
for some p, then the second work point position computing section 49b determines that
calibration is necessary, the computing section 49 proceeds to Step S11, and the calibration
value computing section 49c computes the calibration values.
[0089] In Step S11, the calibration value computing section 49c obtains the evaluation function
F for the work point position computed value (first Zf coordinate) and the datum line
51 (second Zf coordinate). The evaluation function F is assumed as the residual square
sum between the work point position computed value and the datum line 51, and the
calibration value computing section 49c executes the following Equation (23).
[0090] In Step S12, the calibration value computing section 49c performs computation for
updating the angle conversion parameters to be calibrated in such a manner that the
evaluation function F can be minimized. The calibration value computing section 49c
is assumed to use, for example, the steepest-descent method. The parameters to be
calibrated in the q-th (1 ≤ q) repetition process are collected into a vector V[q]
= [αbm βbm αam βam αbk βbk]. The calibration value computing section 49c executes
the following Equation (24) to obtain a Jacobian J from the residual square sum F
and the vector V[q].
[0091] Each partial derivative is computed by the discretization scheme such as the difference
method. The calibration value computing section 49c executes the following Equation
(25) to obtain an updated vector V[q+1] used in the next repetition process from the
Jacobian J and the learning rate η (η > 0) that is the parameter for determining the
convergence speed.
[0092] In Step S13, the calibration value computing section 49c performs convergence determination.
While assuming that elements in the vector V[q] are vk[q] (1 ≤ k ≤ 6) and the convergence
determination threshold is τv, the calibration value computing section 49c executes
the following Expression (26).
[0093] When a condition of Expression (26) is satisfied, the computing section 49 proceeds
to Step S14. Conversely, when the condition of Expression (26) is not satisfied and
time of the repetition processes exceeds set time, the computing section 49 proceeds
to Step S15. Otherwise, the computing section 49 increments q by 1, returns to Step
S16, and continues the repetition processes.
[0094] In Step S14, the parameter update section 49c extracts the calibrated parameters
αbm, βbm, αam, βam, αbk, and βbk from the convergent vector V[q+1], stores the calibrated
parameters in the storage section 41 of the display controller 37 via the input/output
section 48 of the calibration controller 45, and reflects the calibrated parameters
in Computing Equations (1) to (3) used by the angle computing section 40a, and the
computing section 49 ends the flowchart of Fig. 4.
[Effects]
[0095] In the hydraulic excavator 1 configured as described so far, the datum line creation
device 47 is attached to the hydraulic excavator 1. Owing to this, it takes no labor
to install the datum line creation device 47 on the construction site or the like
and no labor to input the gradient of the datum line 51 to the calibration controller
45. Furthermore, the number of times of assuming the calibration posture is reduced
by one from that according to the first embodiment. It is, therefore, possible to
further shorten the calibration work time and further improve the work efficiency,
compared with the first embodiment.
<Third Embodiment>
[0096] A third embodiment of the present invention will next be described. The third embodiment
differs from the first and second embodiments in that the gradient (tilt) and the
position (Zf intercept) of the datum line 51 created by the datum line creation device
47 are both unknown, and in that not only the angle conversion parameters but also
the vehicle body dimension parameter is calibrated.
[0097] Fig. 9 is a side view of the hydraulic excavator 1 according to the third embodiment.
The datum line creation device 47 is configured with a plurality of piles driven in
the ground and a tracing tape tightly stretched between the piles at a desired angle,
and this tracing tape serves as the datum line 51. The datum line information that
indicates a relationship between the coordinate system {Xf, Yf, Zf} of the hydraulic
excavator 1 and the datum line 51 is unknown. A hardware configuration of the hydraulic
excavator 1 according to the present embodiment is the same as that according to the
first embodiment except for the above respects. A flowchart of the calibration process
will be mainly described below.
[0098] Fig. 8 is a flowchart of the calibration process according to the third embodiment
for calibrating the third rotation angle sensor 27 and the length Lbk of the bucket
8, and shows an example of a computation process when the parameters to be calibrated
are assumed as the angle conversion parameters αbk and βbk, the vehicle body dimension
parameter Lbk, and the gradient (θline) and the Zf intercept (Zline) of the datum
line 51.
[0099] First, in Step S21, the computing section 49 sets initial values of αbk, βbk, and
Lbk. The set initial values are theoretical values of the angle conversion parameters
obtained from specified values, an assembly drawing, and the like of the third rotation
angle sensor 27, and a theoretical value of the vehicle body dimension parameter obtained
from a design drawing and the like of the bucket 8. It is noted that Step S21 can
be omitted if the values of αbk, βbk, and Lbk are already set.
[0100] In Step S22, the computing section 49 starts repetition processes for acquiring measurement
values in a plurality of calibration postures. The number N of the repetition processes
needs to be at least equal to the number of the parameters to be estimated. In the
present embodiment, the number N may satisfy N ≥ 5 since the parameters to be estimated
are the parameters to be calibrated and the gradient and the Zf intercept of the datum
line 51. In the present embodiment, it is assumed that N = 5.
[0101] In Step S23, the computing section 49 displays on the display device 18 a message
for urging the operator to cause the work implement 3 to assume a calibration posture
and to operate the operation section 52 in the state.
[0102] In Fig. 9, the work implement 3 assumes three types of calibration postures. All
the N calibration postures assumed by the work implement 3 should differ from one
another.
[0103] In Step S24, the operator operates the operation section 52 at timing at which the
operator operates the vehicle body operating device 17 to drive the boom 6, the arm
7, and the bucket 8 to assume the calibration posture. With operator's operating the
operation section 52 as a trigger, the computing section 49 measures the analog signals
Vbm[p], Vam[p], Vbk[p] from the first to third rotation angle sensors 25 to 27 in
a p-th (1 ≤ p ≤ N) repetition process.
[0104] In Step S25, the computing section 49 determines whether the repetition process starting
at Step S23 has been performed the N times. When determining that the repetition process
has been performed the N times, the computing section 49 ends the repetition processes
and proceeds to Step S26; otherwise, the computing section 49 increments p by 1, returns
to Step S23, and continues the repetition processes.
[0105] In Step S26, the computing section 49 starts repetition processes of Steps S27 to
S32 for obtaining the parameters and the Zf intercept of the datum line 51 to be calibrated
by the nonlinear least-squares method. The repetition processes are continued until
a condition to be described later is satisfied.
[0106] In Step S27, the angle computing section 40a performs angle computation, as represented
by Equations (1) to (3), on the measurement values of the analog signals from the
first to third rotation angle sensors 25 to 27 for the N times, thereby obtaining
angle computed values θbm[p], θam[p], and θbk[p] (1 ≤ p ≤ N) of the boom 6, the arm
7, and the bucket 8.
[0107] In Step S28, the first work point position computing section 40b performs work point
position computation, as represented by Equations (4) and (6), on the angle computed
values for the N times in Step S27, thereby obtaining work point position computed
values Xd[p] and Zd[p] (1 ≤ p ≤ N) on the Xf-Zf plane.
[0108] In Step S29, the second work point position computing section 49b determines whether
calibration is necessary. Determination whether calibration is necessary can be omitted
once the second work point position computing section 49b determines that calibration
is "necessary." When an error of the work point position computed values that are
supposed to be present on the datum line 51 from the coordinates of the datum line
51 is large, the second work point position computing section 49b determines that
calibration is necessary. When the error is small, the second work point position
computing section 49b determines that calibration is unnecessary. The determination
whether calibration is necessary in Step S29 will be described in detail below.
[0109] A linear equation that indicates probable values of a point (Xb, Zb) on the datum
line 51 on the Xf-Zf plane is represented by the following Equation (31). In Equation
(31), it is assumed that θ'line is the angle of the datum line 51 with respect to
the coordinate system of the hydraulic excavator 1 shown in Fig. 9 and Zline is the
Zf intercept of the datum line 51 on the Xf-Zf plane shown in Fig. 9, and that initial
values of the point (Xb, Zb) are (Xb, Zb) = (Xd[1], Zd[1]) and (Xb, Zb) = (Xd[2],
Zd[2]), which are numerical values obtained by substituting the initial values into
Equation (31) and solving simultaneous equations and an inverse trigonometric function.
[0110] The second work point position computing section 49b calculates the second Zf coordinate
by inputting the first Xf coordinate (Xd[p]) into Equation (31) for every p (1 ≤ p
≤ N) .
[0111] When it is assumed that the permissible height error of the work point position computed
value is ΔZ and the following Expression (32) is satisfied for every p (1 ≤ p ≤ N)
(that is, when the magnitude of the difference between the first Zf coordinate (Zd[p])
and the second Zf coordinate does not exceed ΔZ), then the second work point position
computing section 49b determines that calibration is unnecessary and the computing
section 49 ends the flowchart of Fig. 8. Conversely, when Expression (32) is not satisfied
for some p, then the second work point position computing section 49b determines that
calibration is necessary, the computing section 49 proceeds to Step S30, and the calibration
value computing section 49c computes the calibration values.
[0112] In Step S30, the calibration value computing section 49c obtains the evaluation function
F for the work point position computed value (first Zf coordinate) and the datum line
51 (second Zf coordinate). The evaluation function F is assumed as the residual square
sum between the work point position computed value and the datum line 51, and the
calibration value computing section 49c executes the following Equation (33).
[0113] In Step S31, the calibration value computing section 49c performs computation for
updating the angle conversion parameters and the Zf intercept of the datum line 51
to be calibrated in such a manner that the evaluation function F can be minimized.
The calibration value computing section 49c is assumed to use, for example, the steepest-descent
method. The parameters and the Zf intercept of the datum line 51 to be calibrated
in the q-th (1 ≤ q) repetition process are collected into a vector V[q] = [αbk βbk
Lbk θ'line Zline]. The calibration value computing section 49c executes the following
Equation (34) to obtain a Jacobian J from the residual square sum F and the vector
V[q].
[0114] Each partial derivative is computed by the discretization scheme such as the difference
method. The calibration value computing section 49c executes the following Equation
(35) to obtain an updated vector V[q+1] used in the next repetition process from the
Jacobian J and the learning rate η (η > 0) that is the parameter for determining the
convergence speed.
[0115] In Step S32, the calibration value computing section 49c performs convergence determination.
While assuming that elements in the vector V[q] are vk[q] (1 ≤ k ≤5) and the convergence
determination threshold is τv, the calibration value computing section 49c executes
the following Expression (36).
[0116] When a condition of Expression (36) is satisfied, the computing section 49 proceeds
to Step S33. Conversely, when the condition of Expression (36) is not satisfied and
time of the repetition processes exceeds set time, the computing section 49 proceeds
to Step S34. Otherwise, the computing section 49 increments q by 1, returns to Step
S27, and continues the repetition processes.
[0117] In Step S33, the parameter update section 49c extracts the calibrated parameters
αbk, βbk, and Lbk from the convergent vector V[q+1], stores the calibrated parameters
in the storage section 41 of the display controller 37 via the input/output section
48 of the calibration controller 45, and reflects the calibrated parameters in Computing
Equations (1) to (3) used by the angle computing section 40a and Computing Equations
(4) to (6) used by the first work point position computing section 40b, and the computing
section 49 ends the flowchart of Fig. 8.
[0118] In Step S34, the computing section 49 determines that the vector V[q+1] is not convergent,
determines a cause of non-convergence from a computation result of the last repetition
process. When a coping method is discovered from the determined cause, the computing
section 49 displays the coping method on the display section 53 of the calibration
operating device 46, and ends the flowchart of Fig. 8.
[Effects]
[0119] In the hydraulic excavator 1 configured as described so far, it takes no labor to
acquire the gradient of the datum line 51 in advance, and the number of times of assuming
the calibration posture is reduced by two from that according to the first embodiment.
It is, therefore, possible to further shorten the calibration work time and further
improve the work efficiency, compared with the first embodiment.
<Features>
[0120] Features contained in the three embodiments described above will be summarized.
- (1) In each of the above embodiments, a hydraulic excavator includes: a vehicle main
body 2; a multijoint type work implement 3 that is attached to the vehicle main body
2 and configured with a plurality of front implement members 6, 7, and 8; a plurality
of angle sensors 25, 26, and 27 that detect angles of the plurality of front implement
members 6, 7, and 8, respectively; and a display controller 37, the display controller
37 including: an angle computing section 40a that calculates angles of the plurality
of front implement members 6, 7, and 8 on the basis of output signals from the plurality
of angle sensors 25, 26, and 27 and angle conversion parameters (αbm, βbm, αam, βam,
αbk, and βbk); and a first work point position computing section 40b that calculates
a position of a work point 23 arbitrarily set on the work implement 3 on an operation
plane (Xf-Zf plane) of the work implement 3 on the basis of the angles of the plurality
of front implement members 6, 7, and 8 calculated by the angle computing section 40a
and dimension parameters (Lbm, Lam, and Lbk) of the plurality of front implement members
6, 7, and 8. In the hydraulic excavator, when the work implement 3 is actuated in
such a manner that the work point 23 is located at each of a plurality of datum points
on a datum line 51, the first work point position computing section 40b calculates
a position of the work point 23 at each of the plurality of datum points, and a calibration
controller 45 includes: a calibration value computing section 49b that calculates
calibration values of arbitrary parameters included in the angle conversion parameters
(αbm, βbm, αam, βam, αbk, and βbk), the dimension parameters (Lbm, Lam, and Lbk),
and line parameters (tilt tanθ, and intercept Zline) using the fact that the position
of the work point 23 at each of the plurality of datum points calculated by the first
work point position computing section 40b can satisfy an equation (linear equation)
indicating the datum line 51; and a parameter update section 49c that reflects the
calibration values of arbitrary parameters calculated by the calibration value computing
section 49b in computation by a corresponding computing section that is one of the
angle computing section 40a and the first work point position computing section 40b.
- (2) More specifically, in the hydraulic excavator 1 according to (1), the first work
point position computing section 40b calculates a first Xf coordinate and a first
Zf coordinate of the work point 23 at each of the plurality of datum points when the
work implement 3 is actuated in such a manner that the work point 23 is located at
each of the plurality of datum points on the datum line 51, the calibration controller
45 further includes a second work point position computing section 49a that calculates
a second Zf coordinate of the work point 23 at each of the plurality of datum points
by inputting the first Xf coordinate of the work point 23 at each of the plurality
of datum points calculated by the first work point position computing section 40b
into an equation (linear equation) indicating the datum line 51, and the calibration
value computing section 49b calculates the calibration values of the arbitrary parameters
included in the angle conversion parameters, the dimension parameters, and the line
parameters in such a manner that an evaluation equation F (evaluation value) indicating
a dissociation degree between the first Zf coordinate and the second Zf coordinate
at a same datum point among the plurality of datum points is minimized.
If the construction machine is configured as described above, the calibration value
computing section 49b performs numerical analysis in such a manner that an error between
the coordinate value of the work point 23 and the linear equation indicating the datum
line 51 is closer to zero and the parameters are automatically calibrated by making
the work point 23 to be located at the plurality of datum points on the datum line
51. Therefore, it is possible to greatly shorten calibration work time without the
need of measurement and the like of the coordinates of the position of the work point
23 during the calibration work.
- (3) In the first embodiment, the hydraulic excavator further includes, in addition
to the features described in (2), a tilt angle sensor 24 that calculates a tilt angle
θpitch of the vehicle main body 2 with respect to a horizontal plane. The second work
point position computing section 49a sets a difference between a gradient θline of
the datum line 51 with respect to the horizontal plane and the tilt angle θpitch as
a tilt of the datum line 51, and calculates the second Zf coordinate of the work point
23 at each of the plurality of datum points from the equation indicating the line
the tilt of which is set and from the first Xf coordinate of the work point 23 at
each of the plurality of datum points calculated by the first work point position
computing section 40b, the calibration value computing section 49b calculates the
calibration value of the angle conversion parameter and an intercept of the datum
line 51 in such a manner that the evaluation equation F for the first Zf coordinate
and the second Zf coordinate at the same datum point among the plurality of datum
points is minimized, and the parameter update section 49c reflects the calibration
value of the angle parameter calculated by the calibration value computing section
49b in computation by the angle computing section 40a.
In the construction machine configured as described above, the datum line creation
device 47 creates the datum line 51 the gradient θline of which is known, and the
calibration work can be completed only by making the work implement 3 assume calibration
postures by the number obtained by adding one for the intercept of the datum line
51 to the number of angle conversion parameters to be calibrated. Therefore, it is
possible to greatly shorten calibration work time.
- (4) In the second embodiment, the construction machine further includes, in addition
to the features described in (2), a datum line creation device 47 that is attached
to the vehicle main body 2 (upper swing structure 4) and creates a line having a predetermined
gradient θ'line with respect to a horizontal plane as the datum line 51. The second
work point position computing section 49a sets the predetermined gradient θ'line as
a tilt (gradient) of the datum line 51, and calculates the second Zf coordinate of
the work point 23 at each of the plurality of datum points from the equation indicating
the line the tilt of which is set and from the first Xf coordinate of the work point
23 at each of the plurality of datum points calculated by the first work point position
computing section 40b, the calibration value computing section 49b calculates the
calibration value of the angle conversion parameter in such a manner that the evaluation
equation F for the first Zf coordinate and the second Zf coordinate at the same datum
point among the plurality of datum points is minimized, and the parameter update section
49c reflects the calibration value of the angle parameter calculated by the calibration
value computing section 49b in computation by the angle computing section 40a.
In the construction machine configured as described above, the datum line creation
device 47 is attached to the vehicle main body 2. Owing to this, it takes no labor
to install the datum line creation device 47 on the construction site or the like
and no labor to input the gradient of the datum line 51 to the calibration controller
45. Furthermore, the number of times of assuming the calibration posture is reduced
by one from that according to the first embodiment. It is, therefore, possible to
further shorten the calibration work time and further improve the work efficiency,
compared with the first embodiment.
- (5) In the third embodiment, the construction machine is featured, in addition to
the features described in (2), in that the second work point position computing section
49a calculates the second Zf coordinate of the work point 23 at each of the plurality
of datum points from the first Xf coordinate of the work point 23 at each of the plurality
of datum points calculated by the first work point position computing section 40b
and from the equation indicating the line, the calibration value computing section
49b calculates calibration values of an angle conversion parameter and a dimension
parameter of a bucket 8 located at a tip end among the plurality of front implement
members 6, 7, and 8, and a tilt and an intercept of the line in such a manner that
the evaluation equation F for the first Zf coordinate and the second Zf coordinate
at the same datum point among the plurality of datum points is minimized, and the
parameter update section 49c reflects the calibration values of the angle parameter
and the dimension parameter of the bucket 8 calculated by the calibration value computing
section 49b in computation by the angle computing section 40a and the first work point
position computing section 40b.
In the construction machine configured as described above, it takes no labor to acquire
the gradient of the datum line 51 in advance, and the number of times of assuming
the calibration posture is reduced by two from that according to the first embodiment.
It is, therefore, possible to further shorten the calibration work time and further
improve the work efficiency, compared with the first embodiment.
- (6) Moreover, in each embodiment, the construction machine further includes, in addition
to the features according to any one of (1) to (5), a display device 18 that displays
output values (voltage values) from the plurality of angle sensors 25, 26, and 27
in all cases of actuating the work implement 3 in such a manner that the work point
23 is located at each of the plurality of datum points on the datum line 51.
[0121] By so configuring, it becomes easy to make the calibration postures entirely different
from one another when the operator causes the work implement 3 to assume the calibration
postures.
<Others>
[0122] The present invention is not limited to the above embodiments but encompasses various
modifications without departing from the spirit of the invention. For example, the
present invention is not limited to the construction machine that includes all the
configurations described in the above embodiments but encompasses construction machines
from which a part of the configurations is deleted. Furthermore, a part of the configurations
according to some embodiment can be added to or can replace configurations according
to the other embodiment.
[0123] While the bucket 8 is exemplarily described as the work tool in the above embodiments,
the work tool other than the bucket 8 may be used.
[0124] In the above embodiments, the work implement 3 is configured with the boom 6, the
arm 7, the bucket 8, and the boom cylinder 9, the arm cylinder 10, and the bucket
cylinder 11 that drive the boom 6, the arm 7, the bucket 8. However, even when the
number of constituent elements of the work implement 3 increases or decreases, calibration
can be carried out as long as calibration postures equal to or greater, in number,
than the parameters to be estimated are acquired.
[0125] While a case in which the center of the bucket claw tip 22 is set as the work point
23 is exemplarily described in the above embodiments, the work point may be set at
an arbitrary point on any of the work tools (including the bucket 8).
[0126] In the above embodiments, the angle computed values θbm, θam, and θbk of the boom
6, the arm 7, and the bucket 8 are obtained from the first to third rotation angle
sensors 25 to 27. Alternatively, a computation method by calculation of a link from
a stroke length of a cylinder or a computation method using an absolute angle from
a tilt sensor to the gravity may be used.
[0127] In the above embodiments, the linear equations are used for converting the analog
signals detected by the first to third rotation angle sensors 25 to 27 into the angles
and the conversion parameters αbm, βbm, αam, βam, αbk, and βbk are obtained. Alternatively,
the calibration can be carried out using means other than the linear equations as
long as the means is represented by a function of the analog signals to the angles
and acquires the calibration postures equal to or greater, in number, than the parameters
to be estimated.
[0128] In the above embodiments, even if the vehicle body dimension parameters such as the
length Lbm of the boom 6 and the length Lam of the arm 7 are added to the parameters
to be calibrated, the calibration can be carried out as long as the calibration postures
equal to or greater, in number, than the parameters to be estimated are acquired.
[0129] In the above embodiments, it is described that the datum line creation device 47
can be installed at an arbitrary gradient and an arbitrary height. Alternatively,
gradient and height ranges suited for the calibration may be described.
[0130] In the above embodiments, the evaluation function F between the work point position
computed value and the datum line is created while attention is paid to the Zf coordinate.
Alternatively, an evaluation function may be created while attention is paid to the
Xf coordinate.
[0131] In the above embodiments, the steepest-descent method is exemplarily described as
a scheme for deriving parameters for minimizing the evaluation function F by the nonlinear
least-squares method. Alternatively, the other scheme such as the Newton's method
may be used.
[0132] In the above embodiments, the evaluation function F minimized by the nonlinear least-squares
method is exemplarily described as the residual square sum. Alternatively, a sum of
distances between points and lines or a standard deviation may be used.
[0133] In each of the above embodiments, the three controllers 31, 37 and 45 are mounted
in the construction machine. Alternatively, all of or part of these controllers may
be configured into an integral controller. Conversely, a configuration such that functions
of the controllers 31, 37, and 45 are further divided and four or more controllers
are mounted may be adopted.
[0134] Furthermore, in the description in each of the above embodiments, control lines or
information lines considered to be necessary for the description are illustrated but
all the control lines or the information lines related to products are not always
illustrated. In actuality, it may be contemplated that almost all the configurations
are mutually connected.
[0135] Features, components and specific details of the structures of the above-described
embodiments may be exchanged or combined to form further embodiments optimized for
the respective application. As far as those modifications are readily apparent for
an expert skilled in the art they shall be disclosed implicitly by the above description
without specifying explicitly every possible combination, for the sake of conciseness
of the present description.